I have been almost donated a fully reconditioned engine for the wagon. It is a 4.1 EFI, the same as I have now but obviously better

Can anyone advise me on the pitfalls of doing this & what are the main things I have to watch for. The guy I'm getting this off has offered to help me but I want to make sure it all goes according to plan.

Best idea if you and / or the person you are getting you to give you a hand is to get a Workshop Manual. Generally they list reasonably detailed step by tep instructions in removal and installation of engines. They are available from most Auto Parts Retailers.